oh yeah, when i did the speed calculator for my rc18t, it said top speed is 76mph without any tire ballooning.

that little car is RAW, even going in a straight line is hard to do, you have to BABY the throttle up to top speed (which i havent found enough room to top it out[X(]) i punched it from a stand still, and it two seconds, it spun, did a front flip and shot off two tires.

funny thing its only a 4500KV motor with a 28 pinion and 57 spur, but 600watts!! and i still cant gear it down

ok, i'll get off my pedestal

@ shark,

that calculator should have tossed a warning/note at you that above 40-45 it's going to be off as air drag is a huge factor as you get faster
I'm sure your RC is fast, but it's not 76 mph fast

i bet money on that sir. it does atleast 70 no less, the car is also teeny tiny and i have it slammed to the ground with the biggest battery it will fit.
the calculation was also without ballooning.

ive been around rc's for awhile, and when a 3.3 4-tec looks slow, you know its cookin.

check out radarguns.com , they have a nice selection at good prices

Actually, the OP asked for groundspeed AND airspeed...so the pitot-static tube is the answer for airspeed. Also, it will work on a car. As long as the car passes through some sort of medium (air, for instance) the pitot-static probe will work. Just, due to viscous effects and some other things, mount the probe high and forward on your car. Then, drive one direction and turn around and drive the other direction....that'll compensate for wind.
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the pitot tube won't work properly in a car, it's going to get odd readings as it's so close to a solid object (the ground)
and the slower you're going, the larger the error is going to be.. these things were designed to measure aircraft speed and to be accurate in a range of speeds that are much higher than most RC cars are going

Also, if I understand airspeed correctly, a radar gun will not give an aircrafts airspeed but it's groundspeed instead.

My rc18b is pretty darn fast for being such a small car.. Like 30+ fast with a brushed motor so.. Its possible to go 70+

Like I said, though, as long as you mount the pitot-static probe above and in front of your car you'll be fine. Also, the "range of speeds" that the EagleTree is accurate in is 2mph up (I can't remember the top range, but it's up there!)....and if your car isn't capable of doing 2mph it's either a rock crawler or you have some serious issues. Anything above 30mph should give you pretty accurate data, as long as your pitot-static probe is above like 6 inches off the ground. And actually, you could mount it really low so as to negate wind effects.

You know what, now that I think about it...you want the pitot-static probe LOW and out in front so you can call wind effects negligible. Haha, way to use all of your fluid dynamics courses there, Victor! Guess I shoulda thought it through the first time!! Oh well. Point is:

PItot-Static probe low and forward will give you great readings!!
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That is correct! You're taking a reading of an object's velocity with respect to a fixed point on the ground (the radar gun). That's groundspeed.
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I think I found one nearly perfect for my needs:

http://www.radargunsales.com/Speedtr...adar-unit.html

It's not handheld, but rather tripod mounted.

Well, free shipping certainly offsets the $135 that it costs I guess...

I was thinking of a used one via Ebay.

Well, there is one used one on Ebay, about half way down the list of new ones...
http://shop.ebay.com/?_from=R40&_trk...All-Categories
Saves you all of $33 over a new one with a guarentee



It seems you are right.

yeah, it seems like people are willing to go through a lot of trouble and expense to avoid doing 3 math calculations

its always nice with a point and click measurment. the most i would spend on a radar is $30 and i doubt you can get one that cheap.

me, i dont care about actual speed, if its a blur, rips off the tires and takes off like a jet, its fast enough for me.

It's not the math. Even if I thought I could operate a stopwatch and a r/ccar, there's no way I could do that while flying a heli. Good method for little wood cars rolling downhill though.

you could have a friend do it for you

I think it is the math

Ok it's the math.
I don't have friends I can do this with either.
And I like gadgets.